nixos/modules/hardware/video/nvidia: Fix incorrect reference to 'nvidiaSettings'
nixos/modules/hardware/video/nvidia: Fix incorrect reference to 'nvidiaSettings'

This patch fixes a bug caused by an incorrect reference to
'nvidiaSettings' rather than 'cfg.nvidiaSettings'. The bug caused
the system to not build when using the nvidia drivers.

Tested on my local machine.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs